Production of pipe bend sheaths

ABSTRACT

A corrugated plastic or metal foil sheet, for use as an intermediate product in the production of pipe bend sheaths, is longitudinally and transversely arcuately corrugated so that it can be cut longitudinally and transversely into pieces each of which constitutes a sheath in opened shape which can be turned into closed pipe bend shape.

1 PRODUCTION OF PIPE BEND SHEATI-IS This invention relates to theproduction of sheaths for objects having a generally pipe bend shapedouter surface defined by curved inner and outer bend sections, and moreparticularly to the production of pipe bend sheaths which are used forcovering themial insulation, such as foam material, laid on pipes ortubes to be insulated, especially in central heating systems.

A particular form of such sheaths, and their production, is the subjectof my co-pending application whereas the present application Ser. No.224,889 is concerned with the production of a variety of sheaths, notlimited to that particular form, and is based on an intermediateproduct, comprising a specially shaped sheet of flexible resilientlydeformable material, such as a plastic or metal foil or film, from whichsheaths can economically be divided.

According to the invention, a corrugated sheet, for

use as an intermediate product in the production of 20v pipe bendsheaths, consists of flexible resiliently deformable material oflongitudinally and transversely arcuately corrugated form, thecorrugations extending in parallel rows which mutually intersect in thelongitudinal and-transverse directions, each row of corrugations in thelongitudinal direction having a regularly sinuous profile ofsubstantially semicircular alternating hills and valleys, as seen fromeither face of the sheet, and each row of corrugations in the transversedirection having a form which, as seen from one face of the sheet,appears as substantially quadrantal hills altemating with V-shapedvalleys and, as seen from the other face of the sheet, appears assubstantially quadrantal valleys alternating with inverted or saddlebackpass shaped hills. 5

The method in accordance with the invention of producing sheathscomprises cutting a corrugated sheet, as defined above, longitudinallyand transversely into pieces each of which comprises in longitudinalextent substantially the equivalent of -a semicircular hill plus asemicircular valley so that each piece can be resiliently deformed intoan annulus of pipe bend shape.

Alternative ways in which the sheet may be cut and other features of theinvention are included in the following description with reference, byway of example, to the accompanying drawings, in which:

FIGS. la to 0 show in plan, longitudinal section and transverse sectionrespectively a corrugated sheet in accordance with the invention,

FIGS. 2a and b show in plan and side elevation respectively alongitudinal row of corrugations cut from the sheet of FIGS. la to c,and

FIGS. 3, 4, 5 and 6 are longitudinal sections of part of a row ofcorrugations, corresponding to part of FIG. lb or FIG. 2b, illustratingmodifications.

FIG. la shows in plan an embossed corrugated sheet formed, by a pressingor other moulding process, from a plane sheet of foil. This forming iscarried out in such a way that there are produced transverse undulatingcorrugations 30, 32 and longitudinal undulating corrugations 31, 33which succeed one another periodically and symmetrically in parallelrows which mutually intersect in the transverse and longitudinaldirections. The result is that, as seen from either face of the sheet,longitudinal rows of convex corrugation hills, 34 or 37, and concavecorrugation valleys, 35 or 36, are produced, are all substantiallysemicircular as seen in longitudinal section and adjoin one another incontinuous transition. The semicircles correspond in diameter to thepipe diameter of the closed annulus form of the pipe bend sheaths to beproduced. This diameter is substantially that of the pipe, including itsinsulation, to be covered.

In transverse section, the rows' of corrugation hills 34, 37 andcorrugation valleys 35, 36 have the profile of quarter-circlesinterconnected by straight parts 42, 43 which correspond to the ends ofthe pipe bend shape, to connect with adjacent straight lengths of pipesheathing. The corrugation valleys 35,36 correspond, 'when eventuallyinverted, to the throats or inner sides of the bends of eventual sheathsand the corrugation hills 34, 37 eventually form the outer sides of thebends of eventual sheaths.

in FIG. lb, which is a section along the line II in FIG. la, there canbe seen one side of one longitudinal row of corrugations. In FIG. 1c,which is a section on the line IIH in FIG. la, there can be seen oneside of a transverse row of corrugations.

Longitudinally, as shown by FIG. lb, altemately' convex and concavesemicircles adjoin one another to form regular rows of hills and valleysas seen from either side of the sheet. In FIG. 10, successively largeand small quarter-circles are interconnected by straight parts 42, 43 sothat each transverse row of corrugations appears, from one face of thesheet, as alternating quadrantal hills and V-shaped valleys and, fromthe other face, as alternating quadrantal valleys and inverted V orsaddleback pass shaped hills.

If the corrugated sheet is now cut into longitudinal strips, along thechain lines in FIGS. 1a and c, then rows of corrugations are produced,as represented in plan view in FIG. 2a, corresponding to the plan viewin FIG. 1a, and in side elevation in FIG. 2b, similarly to the sectionof FIG. Ib. In the case of the section of FIG. lb, a section surface isobtained which lies in the plane of thedrawing, while with the row ofcorrugations of'FIG. 2b the front edge 44, which intersects.perpendicularly the straight parts 42, lies in a plane oblique to theplane of the drawing. Each longitudinal strip of corrugations, havingbeen cut, through 42 and 43, in mutuallyv perpendicular planesintersecting along the axis of the strip, consists of a quadrantalsector of a hollow body of: sinuous profile.

The individual sheaths are now separated from these rows of corrugationsby cutting the strips across.

By suitable choice of the position of the dividing cuts various forms ofsheaths can be obtained, each in an opened shape which can be turned, byresilient deformation of the material, into a closed shape of pipe bendform.

Ifthe dividing cuts are made straight across at or near the peaks oflongitudinal hills, such as at and 71, then each intervening piece 72constitutes a pipe bend sheath in an opened shape having the form of aquadrantal sector of a hollow body of open-ended hour-glass form as canbe seen in FIG. 2a.

To close the piece of material 72 into pipe bend shape, the convex ends,defined by the cuts 70 and 71, are drawn towards one another so as. toinvert the corrugation valley, or waist portion of the hour-glass shape,the ends closing together to form the outer side of the pipe bend andthe corrugation valley or waist portion the throat thereof. Due to theembossing of the original sheet, the sheath material is stressed so thatit is resiliently stable in both the opened, hour-glass, shape and inthe closed, pipe-bend, shape into which it will snap automatically whenthe valley or waist portion is inverted. This form of sheath isdescribed in more detail in my above-mentioned co-pending applicationand need not be more fully described in this application which isconcerned with the production of sheaths including, but not limited to,that form of sheath.

If dividing cuts are made through thevalley portions, such as at 73 and74, then each intervening piece 75 has the shape somewhat of a helmet orDutch bonnet. If the ends 80 and 81 of a piece 75 are then drawntogether they will invert and meet or overlap to form the throat of apipe bend sheath whilst the hill portion between them forms the outerside of the bend.

Thus, a' longitudinal strip as shown by FIGS. 2a and b can be cut acrossits hills or valleys into pieces each of which comprises in longitudinalextent substantially I the equivalent of a semicircular hill plus asemicircular valley so that each piece can be resiliently deformed intoan annulus of pipe-bend shape.

Preferably the dividing cuts are so positioned that the ends of eachpiece produced will overlap in the closed shape, either at the outsideof the bend for a piece such as 72 or at the throat of the bend for apiece such as 75. For example, the convex end portion of the piece 72cut off at 71 is somewhat longer than the other end. Only a smalldifference is required and the positions of the cuts can changeprogressively along a row so that only occasionally a small longitudinalpiece, of less than sheath length, need be discarded.

The corrugated strips may be cut obliquely, such as at 76 and 77, toproduce sheath pieces, such as 78, of which the ends inversely vary inlength transversely. The oblique ends can, when the sheath is turned toclosed shape, meet with an oblique butt joint or, by a slight helicalconformation of the closed sheath, the oblique ends can be caused tooverlap.

For economy, each corrugated strip will be divided into similar piecesby similarly located straightor oblique transverse cuts, with any slightvariation to obtain overlap, so as to avoid waste by pieces ofincomplete sheath size being left between adjacent cuts. It may howeverbe possible to change from a series of cuts of one kind, such as 70, 71,to another kind, such as 73, 74, by progressive shift in longitudinalposition of the cuts.

In order to provide for overlap of sheath ends without changing theposition of transverse dividing cuts, the embossed shape of theproduction sheet can be modified so as locally to increase thelongitudinal dimensions of the eventual ends of sheaths and thus providefor overlap. The necessary local dimensional increase can be provided bycusps in the curvature of the longitudinal hills or valleys attransverse dividing lines defined by transverse indentations or ridgesrespectively.

In one example, illustrated by FIG. 3, the crests or peaks oflongitudinal hills, such as 34 in FIG. lb, are bulged slightly on eitherside of a transverse cusp 90 which crosses adjacent valleys, such as 35,which ap pear as hills from the other side of the sheet. In themoulding, the cusp 90 may change from one face of the sheet to the otherso as to appear as an indentation or as a ridge at the eventual dividingcut for the respective strip of corrugations.

a The moulding may however be such that transverse ridges are formedacross longitudinal valleys as shown by the cusp 91 in FIG. 4. Ifdividing cuts are made at ridges, such as at 91, the intervening-piecesare of helmet or Dutch bonnet shape and, when closed, overlap at thethroats of their pipe sheath bends.

If it is desired to produce, from one and the same embossed productionsheet, sheaths which are all of the same shape, i.e., all of thehour-glass shape such as 72 or all of the helmet shape such as 75, thenonly short transverse cusps need be formed transversely within eachlongitudinal row, i.e., eventual strip, of corrugations.

The cusps required for helmet-type pieces are shown at 92 and 93 in FIG.5, and by corresponding thick chain lines in FIG. la, extendingtransversely within valleys 35' and 36 of adjacent longitudinal striprows of corrugations from which will be cut sheaths which overlap theirends at the throats of bends.

As shown in FIG. 6, for hour-glass type sheaths, somewhat longertransverse cusps 94 and 95 are made across the crests or peaks of hills34' and 37 of adjacent longitudinal strip rows of corrugations fromwhich will be cut sheaths which overlap their ends at the outer side ofbends.

Sheets which are corrugated for division into pipe bend sheaths asdescribed above may be moulded from any suitable flexible resilientlydeformable material such as plastics foil or film or metal sheet orfoil. I

It will be apparent that sheaths may be produced in a factory bysuccessive sheet-forming and dividing operations or corrugated sheetsmay be produced as intermediate products manufactured as articles forsale to factors or other users who can divide the sheets into sheaths.

I claim:

1. A corrugated sheet useful as an intermediary productin the productionof sheaths for objects having a generally pipe bend shaped externalsurface defined by curved inner and outer. bend sections comprising:

a first plurality of elongated segments, each being of a thin, flexibleresiliently deformable material having an undulating configurationdefining alternate quadrantal hills and substantially V-shaped valleysalong a longitudinal axis and having a semicircular hill-shaped crosssection in a direction transverse to the longitudinal axis;

a second plurality of elongated segments, each being of a thin, flexibleresiliently deformable material having an undulating configurationdefining alternate quadrantal valleys and inverted V-shaped hills alonga longitudinal axis and having a semicircular valley-shaped crosssection in a direction transverse to the longitudinal axis;

the V-shaped valleys and inverted V-shaped hills each having a curvaturewhich is substantially equal to a curvature conforming to the inner bendsection;

the quadrantal hills and quadrantal valleys each having a curvaturewhich is substantially equal to a curvature conforming to the outer bendsection;

said first and second pluralities of elongated segments being adjacentlypositioned with their longitudinal axis in a side-by-side parallel arrayin alternating fashion and being arranged such that the invertedV-shaped hills are centrally aligned with the having ends which willoverlap when closed in pipe bend shape.

3. A corrugated sheet according to claim 2 wherein the cusps extendcontinuously along the elongated segments in a direction parallel tosaid longitudinal axes.

4. A corrugated sheet according to claim 2 wherein the cusps aredisposed parallel to said longitudinal axes and are in alignment along aline transverse to said longitudinal axes.

2. A corrugated sheet according to claim 1 wherein at least some of saidpluralities of elongated segments have cusps therein increasing thedimension of the material on either side thereof thereby enabling thecorrugated sheet to be divided into pieces forming sheaths having endswhich will overlap when closed in pipe bend shape.
 3. A corrugated sheetaccording to claim 2 wherein the cusps extend continuously along theelongated segments in a direction parallel to said longitudinal axes. 4.A corrugated sheet according to claim 2 wherein the cusps are disposedparallel to said longitudinal axes and are in alignment along a linetransverse to said longitudinal axes.